Washington: Scientists have discovered the oldest orchid fossil trapped in amber that dates back some 45 million years to 55 million years. The finding shatters the previous record for an orchid fossil found in Dominican amber about 20-30 million years old. The orchid family has some 28,000 species - more than double the number of bird species and quadruple the mammal species.

Representational image. Wikicommons

"It wasn't until a few years ago that we even had evidence of ancient orchids because there wasn't anything preserved in the fossil record," said George Poinar, professor at Oregon State University in the US. "But now we're beginning to locate pollen evidence associated with insects trapped in amber, opening the door to some new discoveries," said Poinar.

Orchids have their pollen in small sac-like structures called pollinia, which are attached by supports to viscidia, or adhesive pads, that can stick to the various body parts of pollinating insects, including bees, beetles, flies and gnats.

The entire pollination unit is known as a pollinarium. Researchers found a small female fungus gnat that was carrying the pollinaria of an extinct species of orchid when it became trapped in amber more than 45 million years ago. The

The pollinaria was attached to the base of the gnat's hind leg. Amber preserves fossils so well that the researchers could identify a droplet of congealed blood at the tip of the gnat's leg, which had been broken off shortly before it was entombed in amber. At the time, all of the continents had not even yet drifted apart. The fossil shows that orchids were well-established in the Eocene and it is likely that lineages extended back into the Cretaceous period.

The research was published in the Botanical Journal of the Linnean Society.